1. Field of the Invention
This invention generally relates to tactile presenting devices, and more particularly, to a tactile presenting device having the function of presenting a tactile sensation by vibrating a panel for presentation of tactile in a direction perpendicular to the plane surface.
2. Description of the Related Art
Recently, a touch panel has widely been used for personal computers, PDA, ATM equipment, POS terminals, car navigation, copying machines and so on. The touch panel has a flat panel, which may be depressed by a pen or finger, and outputs information indicative of the coordinates of a touched position. The conventional touch panels cannot present a tactile sense (click sense) associated with depressing, which may be presented by mechanical switches, and has a difficulty in presenting recognizable depressing.
Japanese Patent Application No. 2003-122507 discloses a method for presenting a tactile (click sense) sensation by vibrating a panel of a touch panel input device. FIG. 1 shows the touch panel input device disclosed in this application. A piezoelectric element 2 is used as a vibration source, which vibrates movable plates 3 of a touch panel 1.
However, the structure shown in FIG. 1 has a difficulty in low-voltage driving because of the use of the piezoelectric element 2, and needs to boost the ordinary operating voltage for electronic circuits in the range of 3 V to 5 V to hundreds of volts. The piezoelectric element is primarily suitable for high-frequency vibrations, and has small amplitudes of vibration. FIG. 2 shows an exemplary waveform for driving the piezoelectric element. The piezoelectric element vibrates at a frequency of approximately 400 Hz, and this vibration can be heard by ears of human being. The vibration is apparently different from a sense such that the button has been depressed.